Cultures of Two Different Cell Types Are Exposed to the Same

Cultures of two different cell types are exposed to the same signaling ligand.Analysis of gene expression shows that only one of the cell types responded to the ligand.Which of the following may account for this difference?

A) The ligand was only bioavailable to one of the cell types.
B) Only one of the cell types contained accessible target gene DNA sequences.
C) Only one cell type contained DNA.
D) The ligand could only pass through the membrane of one of the cell types.